1. Field of Invention
The present invention relates to transflective liquid crystal devices by which a reflective display that uses light reflected after passing through a liquid crystal layer and a transmissive display that uses light transmitted through the liquid crystal layer can be manufactured, and in which a color filter can be disposed on a light path so that color display can be realized.
2. Description of Related Art
Recently, liquid crystal devices have come into widespread use in electronic devices, such as mobile phones, portable computers, etc. In such liquid crystal devices, reflective liquid crystal devices, in which a light reflecting film is provided on an inside or outside surface of a substrate disposed at the side opposite to the observer""s side of a liquid crystal layer, are known in the art. In reflective liquid crystal devices, light incident from the observer""s side is reflected at the light reflecting film, and is used as a light source for display.
In addition, transmissive liquid crystal devices, in which an illuminating device, that is, a so-called backlight, is disposed at the side opposite to the observer""s side of a liquid crystal layer and is used as a light source for display, are also know in the art. In addition, transflective liquid crystal devices, in which openings are formed in a light reflecting film, and in which reflective display is realized using regions excluding the openings in the light reflecting film and transmissive display is realized using the light passing the openings in the light reflecting film, are also known in the art.
On the other hand, recently, color display is often realized in liquid crystal devices by disposing a color filter having R (red), G(green), and B(blue) or C(cyan), M(magenta), and Y(yellow) subpixels, in a display area of the liquid crystal devices.
According to a known technique of color transflective displays, in which openings are formed in a light reflecting film and a color filter is used, uniform color display over the display area cannot be realized. The inventors have performed various experiments to discover the reason for this, and found that color display cannot be made uniform if the relationship between the openings in the light reflecting film and the R, G, and B or C, M, and Y subpixels regarding position and shape are not adequately coordinated.
In view of the above-described finding, an object of the present invention is to provide a transflective liquid crystal device in which color display can be made uniform over the display surface in both the reflective display mode and the transmissive display mode.
In order to attain the above-described object, according to a first aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter can include a partitioning member, which divides the surface of the substrate into a plurality of sections, and subpixels, which are individually formed in the sections, and openings are formed in the light reflecting film at regions corresponding to thickest parts of the subpixels.
The partitioning member may be formed by, for example, applying an ink-repellent resin at a uniform thickness by a known deposition method, for example, spin coating, and forming a predetermined pattern by a known patterning method, for example, photolithography. In addition, the above-described subpixels are formed by, for example, an inkjet method, that is, by ejecting, in the form of drops, a subpixel material from nozzles of an inkjet head toward the sections devided by the partitioning member.
In the liquid crystal device according to the first aspect of the present invention, as shown in FIG. 5, openings 18 are formed in a light reflecting film 9 at regions corresponding to thickest parts of subpixels 16. Thus, in the reflective display mode, light that passes through the subpixels 16 to and from the light reflecting film 9 at parts excluding the thickest parts of the subpixels 16, as shown by the arrow X0, is used for color display. In addition, in the transmissive display mode, light that passes through the subpixels 16 at thickest parts thereof, as shown by the arrow X1, is used for color display.
Accordingly, light that is transmitted through the subpixels 16 once at the thickest parts thereof is used in the transmissive display mode, and light that is transmitted through the subpixels 16 twice at relatively thin parts thereof is used in the reflective display mode. Accordingly, the optical thickness in the reflective display mode and that in the transmissive display mode can be made close or approximately the same, so that color display can be made uniform between the reflective display mode and the transmissive display mode.
According to a second aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter can include a partitioning member, which divides the surface of the substrate into a plurality of sections, and subpixels, which are individually formed in the sections, and openings are formed in the light reflecting film at regions corresponding to central parts of the sections.
The partitioning member may be formed by, for example, applying an ink-repellent resin at a uniform thickness by a known deposition method, for example, spin coating, and forming a predetermined pattern by a known patterning method, for example, photolithography. In addition, the above-described subpixels are formed by, for example, the inkjet method, that is, by ejecting, in the form of drops, a subpixel material from nozzles of an inkjet head toward the sections.
As shown in FIG. 5(a) and FIG. 5(c), in the case in which the subpixels 16 are formed by the inkjet method, the subpixels 16 tend to swell upward at central regions of the sections divided by a partitioning member 14. Accordingly, when the openings 18 are formed in the light reflecting film 9 at regions corresponding to the central parts of the sections divided by the partitioning member 14, the optical thickness in the reflective display mode and that in the transmissive display mode can be made close or approximately the same. Thus, color display can be made uniform between the reflective display mode and the transmissive display mode.
According to a third aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter can include a partitioning member, which divides the surface of the substrate into a plurality of rectangular sections, and subpixels, which are individually formed in the rectangular section, and openings are formed in the light reflecting film in such a manner that the openings extend in the longitudinal direction of the rectangular sections.
The partitioning member may be formed by, for example, applying an ink-repellent resin at a uniform thickness by a known deposition method, for example, spin coating, and forming a predetermined pattern by a known patterning method, for example, photolithography. In addition, the above-described subpixels are formed by, for example, the inkjet method, that is, by ejecting, in the form of drops, a subpixel material from nozzles of an inkjet head toward the sections.
Generally, in order to realize color display, especially full-color display, a unit including R, G, and B subpixels functions as a pixel, and a full-color image is displayed by controlling the color illuminated in each pixel. The R, G, and B subpixels are often formed in a rectangular shape. In such a case, as shown in FIG. 5(b), the partitioning member 14 forms a plurality of rectangular sections, and the subpixels 16 are individually formed in the sections.
In the case in which the subpixels 16 are formed in the rectangular shape as seen from top, the openings 18 are preferably formed in a rectangular shape that extends in the longitudinal direction of the subpixels 16. Accordingly, in the transmissive display mode, sufficient amount of light that is uniform in the longitudinal direction of the subpixels 16 can be supplied to the subpixels 16, so that uniform color display can be realized.
According to a fourth aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter can include a partitioning member, which divides the surface of the substrate into a plurality of sections, and subpixels, which are individually formed in the sections, and openings are formed in the light reflecting film in such a manner that the openings have a shape corresponding to the thickness distribution of the subpixels.
The partitioning member may be formed by, for example, applying an ink-repellent resin at a uniform thickness by a known deposition method, for example, spin coating, and forming a predetermined pattern by a known patterning method, for example, photolithography. In addition, the above-described subpixels are formed by, for example, the inkjet method, that is, by ejecting, in the form of drops, a subpixel material from nozzles of an inkjet head toward the sections.
In the case in which the subpixels are formed by supplying ink, that is, a subpixel material to the sections divided by the partitioning member, the thickness of the subpixels may not be uniform. For example, as shown in FIG. 5(a) and FIG. 5(c), the subpixels 16 may be formed in a convex shape, in other words, shaped like a dome. When the thickness of the subpixels 16 is not uniform, the openings 18 are preferably formed only at regions corresponding to the parts of the subpixels 16 where the thickness thereof is larger than a reference value T0. Accordingly, the color display can be made more uniform between the reflective display mode and the transmissive display mode.
In the case in which the openings are formed in the light reflecting film in the shape corresponding to the thickness distribution of the subpixels, the shape of the openings is effectively determined utilizing light interference fringes. More specifically, as shown in FIG. 8(a), natural light R0 is radiated on the subpixel 16, and light reflected form the light reflecting film 9 is photographed by a camera 30. Then, when the photographed image is displayed, interference fringes F, which are schematically shown in FIG. 8(b), are obtained in accordance with the thickness distribution of the subpixel 16. The interference fringes F can be assumed as contour lines of the subpixel 16. Accordingly, when the openings 18 are formed in the light reflecting film in the shape of one of the interference fringes F which are selected, the openings having a shape that accurately corresponds to the thickness distribution of the subpixels can be obtained.
In the liquid crystal device according to one of the above-described first to fourth aspects of the present invention, the openings preferably have a planner shape such that the corners thereof are cut off. For example, the corners of the openings may be formed as beveled corners M1 shown in FIG. 6(b), rounded corners M2 shown in FIG. 7(b).
The subpixels formed in the sections divided by the partitioning member tend to have a convex shape such that the central parts thereof are thick and the peripheral parts thereof are thin. In addition, the surfaces of the subpixels are curved in three-dimensional space along the diagonal lines of the sections. In such a case, when the corners of the openings in the light reflecting film are formed in an angular shape of, for example, 90xc2x0, uniformity of color may be degraded at the corners of the openings. In contrast, when the openings have a shape such that the corners thereof are cut off as described above, uniform color distribution can be obtained.
In addition, in the liquid crystal device according to one of the above-described first to fourth aspects of the present invention, the planner shape of opening may have a rectangular shape, an oval shape, or an elliptical shape. The elliptical shape is a shape in which the corners of a rectangle are rounded in a certain way, and the oval shape is a shape excluding the elliptical shape that can also be obtained by rounding the corners of a rectangle. When the openings are formed in one of the above-described shapes, color display can be made more uniform compared with the case in which the openings are formed in a square shape.
In addition, in the liquid crystal device according to one of the above-described first to fourth aspects of the present invention, the area of a single opening is 5% to 30%, and preferably about 20% of the area of a single section. When the aperture ratio is in the above-described range, satisfactory visibility can be achieved in both the reflective display mode and the transmissive display mode. When the aperture ratio is larger than the above-described range, display can become unclear since a sufficient amount of reflected light cannot be obtained by an illuminating device. When the aperture ratio is smaller than the above-described range, the display can become unclear since sufficient illumination cannot be obtained.
According to another aspect of the present invention, a manufacturing method for a liquid crystal device, in which liquid crystal is sandwiched between a pair of substrates, at least one of which includes a color filter, can include forming a light reflecting film on one of the substrates, forming a partitioning member which divides the surface of the substrate into a plurality of sections, and forming subpixels in the sections divided by the partitioning member. The step of forming the subpixels can further include ejecting, in the form of drops, a material for forming the subpixels from nozzles toward the sections and the step of forming the light reflecting film includes the step of forming openings in the light reflecting film at regions corresponding to the sections.
In the manufacturing method for the liquid crystal device according to the present invention, each subpixel can be formed by the inkjet method. Thus, the relationships between the openings formed in the light reflecting film and the subpixels can be individually adjusted, so that the colors displayed by the subpixels can be individually and precisely adjusted. Accordingly, uniform color display over the display area can be realized.
In the manufacturing method for the liquid crystal device according to the present invention, the openings can be formed in the light reflecting film at regions corresponding to thickest parts of the subpixels in the step of forming the light reflecting film. Accordingly, light that is transmitted through the subpixels once at the thickest parts thereof is used in the transmissive display mode, and light that is transmitted through the subpixels twice at relatively thin parts thereof is used in the reflective display mode. Accordingly, the optical thickness in the reflective display mode and that in the transmissive display mode can be made closer or approximately the same, so that color display can be made uniform between the reflective display mode and the transmissive display mode.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the openings are preferably formed in the light reflecting film at regions corresponding to central parts of the sections in the step of forming the light reflecting film. As shown in FIG. 5(a) and FIG. 5(c), in the case in which the subpixels 16 are formed by the inkjet method, the subpixels 16 tend to swell upward at central regions of the sections divided by the partitioning member 14. Accordingly, when the openings 18 are formed in the light reflecting film 9 at regions corresponding to the central parts of the sections divided by the partitioning member 14, the optical thickness in the reflective display mode and that in the transmissive display mode can be made close or approximately the same. Thus, color display can be made uniform between the reflective display mode and the transmissive display mode.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the surface of the substrate may be divided into a plurality of rectangular sections in the step of forming the partitioning member. In such a case, the openings are preferably formed in the light reflecting film in such a manner that the openings extend in the longitudinal direction of the rectangular sections in the step of forming the light reflecting film. Accordingly, in the transmissive display mode, a sufficient amount of light that is uniform in the longitudinal direction of the subpixels can be supplied to the subpixels, so that uniform color display can be realized.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the openings are preferably formed in the light reflecting film in such a manner that the openings have a shape corresponding to the thickness distribution of the subpixels in the step of forming the light reflecting film. In color display, density of color is significantly effected by the thickness of the subpixels. Thus, uniformity of color density can be degraded when the openings are formed irrespective of the thickness distribution of the subpixels. In contrast, uniform color display can be obtained when the shape of the openings is determined based on thickness distribution of the subpixels.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the openings having a shape such that the corners thereof are cut off are preferably formed in the light reflecting film in the step of forming the light reflecting film. The subpixels formed in sections divided by the partitioning member tend to have a convex shape such that the central parts thereof are thick and the peripheral parts thereof are thin. In addition, the surfaces of the subpixels are curved in three-dimensional space along the diagonal lines of the sections. In such a case, when the corners of the openings are formed in an angular shape of, for example, 90xc2x0, uniformity of color may be degraded at the corners of the openings. In contrast, when the openings have a shape such that the corners thereof are cut off as described above, uniform color distribution can be obtained.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the planner shape of opening having a rectangular shape, an oval shape, or an elliptical shape are preferably formed in the light reflecting film in the step of forming the light reflecting film. The elliptical shape is a specific shape in which the corners of a rectangle are rounded in a certain way, and the oval shape is a shape excluding the elliptical shape that can also be obtained by rounding the corners of a rectangle. When the openings are formed in one of the above-described shapes, color display can be made more uniform compared with the case in which the openings are formed in a square shape.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the openings are preferably formed in the light reflecting film in such a manner that the area of a single opening is 5% to 30%, and preferably about 20% of the area of a single section in the step of forming the light reflecting film. When the aperture ratio is in the above-described range, satisfactory visibility can be ensured in both the reflective display mode and the transmissive display mode. When the aperture ratio is larger than the above-described range, display becomes unclear since a sufficient amount of reflected light cannot be obtained. When the aperture ratio is smaller than the above-described range, the display becomes unclear since sufficient illumination cannot be obtained by an illuminating device.
In the liquid crystal device according to the present invention, the subpixels may be formed in a convex shape such that the central parts thereof swell upward.
In the manufacturing method for the liquid crystal device according to the present invention, the subpixels may be formed in a convex shape such that the central parts thereof swell upward.
According to another aspect of the present invention, a liquid crystal device comprises a pair of substrates which sandwich liquid crystal; a light reflecting film formed on at least one of the substrates; and a color filter formed on the light reflecting film. The color filter can include a partitioning member, which divides the surface of the substrate into a plurality of sections, and subpixels, which are individually formed in the sections. The subpixels are formed in a concave shape such that the central parts thereof are hollow, and openings are formed in the light reflecting film at regions corresponding to thickest parts of the subpixels.
According to another aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter includes a partitioning member, which divides the surface of the substrate into a plurality of sections, and subpixels, which are individually formed in the sections. The subpixels are formed in a concave shape such that the central parts thereof are hollow, and openings are formed in the light reflecting film at regions corresponding to part of peripheral parts of the sections in such a manner that the peripheral parts of the sections are partly or entirely covered by the openings.
According to another aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter includes a partitioning member, which divides the surface of the substrate into a plurality of rectangular sections, and subpixels, which are individually formed in the rectangular sections. The subpixels are formed in a concave shape such that the central parts thereof are hollow, and, and openings are formed in the light reflecting film in such a manner that the openings extend in the longitudinal direction or the lateral direction of the rectangular sections at regions corresponding to peripheral parts of the rectangular sections.
According to another aspect of the present invention, a liquid crystal device can include a pair of substrates which sandwich liquid crystal, a light reflecting film formed on at least one of the substrates, and a color filter formed on the light reflecting film. The color filter includes a partitioning member, which divides the surface of the substrate into a plurality of sections, and subpixels, which are individually formed in the sections. The subpixels are formed in a concave shape such that the central parts thereof are hollow, and openings are formed in the light reflecting film in such a manner that the openings have a shape corresponding to the thickness distribution of the subpixels.
In the manufacturing method for the liquid crystal according to the present invention, the subpixels may be formed in a concave shape such that the central parts thereof are hollow in the step of forming the subpixels, and the openings may be formed in the light reflecting film at regions corresponding to thickest parts of the subpixels in the step of forming the light reflecting film.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the subpixels may be formed in a concave shape such that the central parts thereof are hollow in the step of forming the subpixels, and the openings may be formed in the light reflecting film at regions corresponding to peripheral parts of the sections in such a manner that the peripheral parts of the sections are partly or entirely covered by the opening in the step of forming the light reflecting film.
In addition, in the manufacturing method for the liquid crystal device according to the present invention, the subpixels may be formed in a concave shape such that the central parts thereof are hollow in the step of forming the subpixels, and the openings may be formed in the light reflecting film at regions corresponding to peripheral parts of the rectangular sections in such a manner that the openings extend in the longitudinal direction or the lateral direction of the rectangular sections in the step of forming the light reflecting film.
In addition, in the manufacturing method of the liquid crystal device according to the present invention, the subpixels may be formed in a concave shape such that the central parts thereof are hollow in the step of forming the subpixels, and the openings may be formed in the light reflecting film in such a manner that the openings have a shape corresponding to the thickness distribution of the subpixels in the step of forming the light reflecting film.
According to another aspect of the present invention, an electronic device comprises a liquid crystal device which is constructed as described above and a housing which contains the liquid crystal device.